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I am considering an upgrade to my Image 34i integrated amplifier(China). At first (5 years ago when I received it) I liked it a lot for its air, imaging and musicality. Now I have other amps that are clearly better. There is no way to sell it locally (nobody knows this brand). Some people say that I must replace the stock resistors with carbon ones but I don't know proper brands (Dale, AB, Vishay?)
Any help will be appreciated.
Follow Ups:
Anyone who says changing resistors is unproductive is way off the mark. It looks like Michael Samra has some very good suggestions at least based on experiance. Lots of opinions on the sound of resistors out there. Michaels responce looks very good. Tweaker
What many audiophilea never ask themselves when wish to upgrade or mod their equipment is,what do you expect the mods or upgrades to accomplish?
This is a very basic amp that is built decent for the price but the only thing I can see to do is,put in film cap power supply caps as that will widen the bandwidth somewhat and give you a little better bass and more extension on the highs..Even if you use one film cap in the first section,it will help..
The reason this amp has all metal film resistors in it no doubt is because it uses EL34s...The metal films are a little bit more quiet and being the EL34s are not that extended at either end in comparison to say a 6L6gc, or an EL37,or an EL84,having all metal films aids in definition but you sacrifice openness and realism when you use all metal film resistors..At the very least,you want 1k carbon comp resistors on the grid stoppers of the EL34s between pins 5 and 6. The other thing I would do is lose the 12Au7s and wire the socket filaments to use 6CG7s.That is a huge gain because the 6CG7 is more linear than the 12AU7 and it has a higher plate dissipation and lower distortion.
Outside of you changing your output transformers and redesigning the power supply which are excellent suggestions,this is what I would do on this amp unless you want to put lots of money into it.The film cap supply even if you run 35uf film caps as bypasses as I did on the amp below,that will help you a lot...
The 6CG7 tubes and the Carbon Comp for the grid stoppers will widen the bandwidth and give you more definition,realism,and openness.Triode connecting EL34s help a lot if you don't need the extra power.
Look at how I did the amp below.You can see the three 35uf film caps which I used as bypass caps which essentially took over the filtering and energy delivery duties for the amp being they are ultra low ESR and very fast..The electrolytics on super heavy transients are there to keep it from seeing the rail DC under extreme dynamic conditions.
I Also put teflon caps in this amp so if you feel you are lacking definition and dynamics,the FT2s do a wonderful job..That can be the 4th thing you do...Just ask yourself what you don't like about your amp and go from there.I did a few other things to the Sophia below but basically upgrading and only slight modding.
Original
with upgrades including Schotkys and FT2 Teflon caps,and film cap bypasses.
"
Honest amplification is better than excessive 2nd order distortion anytime.
Edits: 08/13/14
Mike,
Re film cap power supply caps:
My tech asks - Do you suggest that I replace the power supply caps (blue colored Philips caps made in Mexico) with power supply film caps or that I place film caps in parallel in addition to the stock caps? He says it's exactly what you did to the Sophia amp...
akolegov, I would not attempt to do all the changes at once. You may want to start out by replacing those coupling caps, with some better versions, and maybe adding a byppass to the main filter caps (blue cans). Then give it a listen and see what you think before doing more work on the amp.
The sonics are the sum of all the parts, resistors, caps, transformers, tubes, etc.
It's very likely that 95% of the needed improvement lies with the output transformers and power supply. Unless you want to revamp nearly the entire amplifier, I would sell it and move on.
--------------------------
Buy Chinese. Bury freedom.
That's what I am trying to do...
Try swapping output transformers, triode wiring the finals, and removing the global negative feedback loop.
What is going to make the amp better is an improvement in (rough order of importance):
1. Circuit
2. Transformers
3. Capacitors
4. Electro/Mechanical (RCAs, layout, etc)
5. Resistors
Putting in KOAs is not going to turn the amp into a different animal.
Much easier to sell an amp that has not been messed with. If you have any plans of selling, sell. Otherwise it is kind of like putting magnesium racing wheels on a Chevy Malibu, yes they are better wheels but you are still driving a Malibu.
I don't know what KOAs are but I feel sure that replacing the existing resistors with carbon types would do no good. That seems s very odd suggestion
Like These
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Mike,
I replaced almost all of the original carbon comp resistors in my Mc240 with metal film.Could that explain why the amp doesn't sound as warm now?
~!
The Mind has No Firewall~ U.S. Army War College.
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